1. Field of the Invention
This invention relates generally to telecommunications, and more particularly, to wireless communications.
2. Description of the Related Art
The wireless industry and the Internet are converging. In wireless cellular technology, this convergence is embodied in Time Division Multiple Access (TDMA) based technology, particular beginning with second-generation systems, such as the European Telecommunications Standards Institute (ETSI) General Packet Radio Service (GPRS). Alternatively, in Code Division Multiple Access (CDMA) based systems, this convergence is achieved via new standards, such as 3rd Generation Partnership Project's (3GPP's) Universal Mobile Telecommunications System (UMTS) standard or via the evolution of existing Second Generation (2G) CDMA standards, such as IS95 in the form of CDMA 2000. These systems are intended to convey data as well as legacy voice traffic. Looking to the future, new communication systems are in the process of being defined and are currently termed fourth generation systems (4G). These 4G systems are typically characterized by high bandwidths and small cell size. The aim of these 4G systems is to be able to provide Internet connectivity, including transparent access to the Internet, while also providing a plethora of services and applications seamlessly via a variety of air interfaces to the users while the user roams around the variety of cellular systems. This type of future scenario is very heterogeneous in characteristic and is captured by the International Telecommunication Union Radiocommunication sector (ITU-R).
These proposed 4G systems suffer from a variety of shortcomings, including the fact that the current cellular architectures will be required to be heavily modified to provide desired interconnectivity and services. These modifications will result in cellular architectures that are exceedingly complex, and thus, expensive to construct and maintain.
A standard approach to providing cellular access involves adopting a hierarchical architectural approach to gain access to Public Switched Telephone Networks (PSTNs) or the Internet. This type of solution is epitomized through the presentation and management of a variety of interfaces that add to the complexity of the system. In these architectures, the entry point to the system is physically remote from the exit point at the air interface. Moreover, typically, Radio Link Protocols (RLP) that characterize the type of cellular system are split over two or more network elements. For example, the RLP is split between the base station (BTS or NodeB) and the Radio System/Network Controller (RSC/RNC). Additionally, the control elements of these networks are again split over a number of network elements. For example, in a Global System for Mobile communications (GSM) system the control elements are distributed over the Base Station Controllers (BSCs) and the Mobile-services Switching Center (MSC), or in the case of GPRS, the control elements are distributed over the BSC and the Serving GPRS Support Node (SGSN). In UMTS, a similar split would occur over the RNC and MSC for voice traffic or the RNC and SGSN for packet data. As can be seen, there are splits in both the control and user planes. These splits were originally implemented to solve technological problems that arose from limited processing power and the limited availability of bandwidth of transmission systems between the network elements. These splits imply that it was desirable to have the RNC oversee many BTSs. Similarly, a number of RNCs are controlled by a central data distributor, such as the MSC or the SGSN. In short, past processing capabilities were sufficiently expensive that for the cellular system to be viable, the processing had to be split across a variety of network elements.
There have been other approaches in wireless connectivity that have principally addressed the need for broadband wireless access, such as Hiperlan, and 802.11 based systems. Some prior attempts have tried to tie in cellular aspects to the general idea of broadband access but they did not address the backward compatibility of the air interfaces, while the others are mainly directed to the Media Access Control (MAC) layer and the physical layer and do not address the generic aspects of cellular systems in regard to radio resource management or mobility across a controlled cellular network. Both systems could be considered as orthogonal systems that are provided to complement the cellular network, and hence cannot be considered as a simplification to the cellular system.
Generally, there are at least three significant shortcomings associated with the solutions described above. First, scalability of the system is significantly limited. In a traditional cellular network, increased capacity of the system may be obtained by adding BTSs. BTSs, however, may not be simply added to the system without eventually creating a need for additional elements in the system. For example, as the capacity of RNCs becomes saturated, the addition of another BTS would require more RNCs. This argument also recurses upward to the MSCs, SGSNs, etc. Accordingly, this approach has a relatively high cost with regard to the amount of equipment needed to build the solution as capacity limits are reached. Moreover, this problem will also be exacerbated by the tendency toward small cells as advocated by prior systems. Also, a new BTS will start off supporting a lighter load than the existing BTSs, thereby leading to inefficient use of the resources in the wireless network.
Second, flexibility of the system is significantly limited. The second problem with traditional cellular networks is that the existing solutions are not designed to allow the use of equipment using different radio interfaces. That is, although provision is made to hand-over from other radio interfaces, direct access to future types of interfaces is not provided.
Third, the system becomes exceedingly complex. Both of the above problem areas combine to make the present solutions complex or at least overly complicated in the sense of future development of a network. That is, each new generation typically requires that a new infrastructure be developed, such as in the case of UMTS. This complexity may then necessitate high capital expenditures to create the new infrastructure. A second form of complexity arises out of the management of the numerous interfaces that these systems present. This type of complexity is reflected in higher operational expenditures.
Wireless communications systems are becoming an increasingly integral aspect of modem communications. To ensure Quality of Service (QoS) and end-user satisfaction, efficient resource allocation and management strategies are required. While traditional wireless networks have primarily carried voice traffic, current and next-generation wireless networks are becoming increasingly data-centric due to the increased popularity of data applications using protocols such as the Transmission Control Protocol (TCP). As such, future wireless networks must increasingly be able to efficiently allocate resources between both voice and data traffic. However, such efficiency can be difficult to achieve because data applications are fundamentally different from traditional voice applications, both in terms of the traffic characteristics and the QoS requirements. This difference stems from the fact that, in general, voice applications typically require a constant transmission rate, independent of the network loading and the wireless channel quality. Reliable communication in such voice applications is generally achieved through power control to alleviate adverse channel conditions. On the other hand, in data applications, performance as perceived by the end-user is closely related to the network-layer throughput, the transaction time for initiating a connection and the transaction time for transmitting the data. Both the throughput and transaction time for data transmissions are dependent upon the channel quality, the network load and the resource allocation (scheduling) strategy.
Data applications are typically more delay-tolerant than voice applications and are able to accept a marginal increase in delay to achieve improved long-term throughput and greater energy efficiency. For example, email communications are much less sensitive to delays and interruptions in transmission than are voice communications. Internet access and file transfers, likewise, can tolerate a bursty communications channel, as long as reasonable response times and reasonable average throughputs are maintained. Further, due to increased buffering typically available on data devices relative to voice devices, and due to the substantially unidirectional nature of the communications, even streaming data applications exhibit a greater robustness to data interruptions than do voice communications. This relatively high delay tolerance of data traffic, in addition to the bursty nature of data traffic (i.e., packets of data in a transmission tend to be transmitted in bursts), allows for flexible transmission scheduling strategies to achieve greater efficiency of the limited network resources.
The present invention is directed to overcoming, or at least reducing, the effects of, one or more of the problems set forth above.